refactoring

Yavsc/Helpers/BillingHelpers.cs

@@ -1,6 +1,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using Yavsc.Billing;
+using Yavsc.Models.Billing;
 
 namespace Yavsc.Helpers
 {
@@ -8,5 +9,7 @@ namespace Yavsc.Helpers
     {
         public static decimal Addition(this List<IBillItem> items) => items.Aggregate<IBillItem, decimal>(0m, (t, l) => t + l.Count * l.UnitaryCost);
 
+         public static decimal Addition(this List<CommandLine> items) => items.Select(i=>((IBillItem)i)).ToList().Addition();
+
     }
 }